A thermoplastic resin has a lower specific gravity than glass or metal, has excellent properties in terms of moldability and impact resistance, and is thus useful as materials for a housing of electric/electronic products, automotive interior/exterior materials, and exterior materials for construction. Particularly, with the trend of reducing weight and thickness of electric/electronic products, plastic products using such a thermoplastic resin are rapidly replacing glass or metal products.
For example, a polyester resin such as polyethylene terephthalate (PET) has excellent properties in terms of weather resistance, impact resistance, chemical resistance, and gloss and is widely used in various fields.
However, polyethylene terephthalate is hydrolyzed at high temperature, has low glass transition temperature, and is thus unsuitable for use in components requiring high heat resistance, such as electric/electronic products or automotive interior/exterior materials.
In order to overcome these problems, there has been proposed a method in which fillers such as glass fibers or crystalline polyester resins such as polybutylene terephthalate are added to improve heat resistance of a polyester resin. However, a polyester resin prepared by this method can have low flowability and thus poor moldability. Although reducing the amount (content) of glass fibers or reducing molecular weight of a crystalline polyester resin can improve flowability of a polyester resin, these methods can reduce impact resistance of the polyester resin, causing the resin to be vulnerable to external impact. Therefore, there is a need for a polyester resin composition which exhibits excellent properties in terms of both flowability and impact resistance.